To cook the duck breast:

1. Preheat the oven to 190C.
2. Using a sharp knife score the skin and season with salt and pepper. 
3. Heat a pan until you can feel moderate heat and place the duck, skin side down into the pan for 5 minutes until golden. Turn the duck breast over and cook for 2 minutes.
4. Place the duck in a roasting tray and cook in the oven for 8 minutes. Remove the duck and let this rest for at least 5 minutes before slicing into it.

Salsa verde

1. Place all the parsley leaves in a food processor and pulse until finely chopped.
2. Add the capers, anchovies, mustard and garlic and mix in food processor.
3. Slowly drizzle in the oil and vinegar. The salsa should not be too liquid. Season with the salt. Transfer to a sterilized jar and refrigerate.
4. Spoon a couple of tablespoons os salsa verde onto each plate and top with sliced duck breast. Serve with dressed butter lettuce leaves.